The present invention relates to a novel vinylidene fluoride copolymer having functional groups which is excellent in weatherability and is compatible with an acrylic resin, so which is suitable for use as coatings, sealing materials or raw materials for moldings such as films, a curable composition containing the same, and a coating composition comprising the same and an acrylic resin as main components.
Polyvinylidene fluoride (homopolymer of vinylidene fluoride) (PVDF) is, as well known, excellent in weatherability, chemical resistance and corrosion resistance. Further, PVDF is excellent in mechanical properties and processability, so it has been widely applied to various uses such as moldings, films and coatings. Particularly, when PVDF is used as the coating, PVDF is blended with a methyl methacrylate copolymer having good compatibility with PVDF for improving the light permeability.
Only solvents having very high polarity and a high boiling point such as N,N-dimethylformamide and N,N-dimethylacetoamide can dissolve PVDF because of high crystallinity. Accordingly, the use of PVDF as the coating is restricted. That is, a dispersion-type of an organosol wherein PVDF is dispersed in water or an organic solvent coating and a powdery coating have been put on the market. Both the coatings, however, require to treat the film at a high temperature for fixing the film after coating. Recently, an alternating copolymer of chlorotrifluoroethylene or tetrafluoro-ethylene and a vinyl ether or vinyl ester wherein crosslinkable and functional groups are incorporated into a part of the vinyl ether begins to be used as a curable fluorocarbon resin coating at room temperature which has an excellent weatherability (Japanese Examined Patent Publication No. 60-21686 and Japanese Unexamined Patent Publication No. 59-102962). Although the coatings as disclosed in the publications are improved in workability, they are inferior to the PVDF coatings in weatherability, stain resistance, corrosion resistance, and the like.
An object of the present invention is to provide a vinylidene fluoride copolymer having excellent solvent solubility, excellent compatibility with an acrylic resin alike PVDF, and functional groups curable at room temperature.
A further object of the present invention is to provide a curable composition comprising the above-mentioned vinylidene fluoride copolymer and a curing agent.
A still further object of the present invention is to provide a coating composition comprising the above-mentioned vinylidene fluoride copolymer and an acrylic resin which is capable of giving a film having excellent weatherbility, stain resistance and glossiness.
These and other objects of the present invention will become apparent from the description hereinafter.